1. Field of the Invention
This invention relates to evaporative coolers and more particularly to an improved automatic flushing and draining apparatus for use with evaporative coolers .
2. Description of the Prior Art
Evaporative coolers of the type having an air handler mounted in a cabinet for drawing air into the cooler through wettable cooler pads and delivering the evaporatively cooled air to a point of use, have the necessary water supply contained within a floor pan or sump. The water level within the sump is maintained at a predetermined level by a float controlled inlet valve that is suitably connected to a source of water under pressure, such as a domestic water line. A pump is mounted in the sump and operates to supply water to the cooler's water distribution system which in turn distributes the water to the cooler pads. The wet cooler pads will cool the air being drawn therethrough by the air handler in accordance with the well known evaporative principle, and the unevaporated water will drain under the influence of gravity from the pads and return to the sump.
During such operation, the water, which inherently contains minerals, such as sodium and calcium chlorides and other impurities, will increase as to its concentration of those minerals due to the evaporation process. As the mineral concentration increases, the rate of precipitation will also increase which results in mineral deposits, or scaling, of the various cooler components. Such mineral deposition causes calcification of the cooler pads, clogging of the water passages, corrosion of the metal and the like, but the most serious problem is with the electric motors and wiring. When the mineral salts, which are electrovalent compounds, are deposited on the wiring terminals, and the various parts of the electric motors themselves, they attack those components and cause premature failures. Further, those compounds are hygroscopic in nature and will thus attract moisture out of the atmosphere even when the evaporative cooler is inoperative, and thus, salt induced deterioration is a continuing process. To keep such mineral deposits to a minimum, the cooler should be periodically drained, flushed, and refilled with fresh water. However, since such draining, flushing and refilling is something which should be accomplished on a regular and a rather frequent schedule, as determined by the characteristics of the water, it is something that is almost always forgotten, or simply ignored.
The above described problem of mineral deposition is compounded by the fact that the water is stored within the sump which serves as a reservoir. Thus, the various cooler components are exposed to a relatively large body of water in the bottom of its cabinet. Unless the sump is drained at the end of a cooling season, or prior to other periods of nonuse, such direct exposure of the components to the water body is something that can, and often is, continuous whether the cooler is operating or not. Draining of the sump preparatory to a period of nonuse is no guarantee that the sump will remain dry for the period of nonuse in that leakage from the inlet supply line and/or rain entering the cooler cabinet through the pads will collect in the sump.
The above described problems and shortcomings of prior art evaporative coolers is something that has long been recognized and various attempts have been made to solve, or at least, minimize some of those problems. For example, devices which dispense chemicals into the water to reduce mineral concentration and deposition problems have been suggested, however, such devices have not received widespread commercial acceptance due to the minimal benefits derived, cost, and the maintenance requirements.
One particular prior art device has been suggested in U.S. Pat. No. 2,828,761, for automatically draining, flushing, and replacing the water in the cooler's sump and for draining a large portion of the water therefrom when the inlet water supply to the sump is shutoff. Briefly, this prior art device includes a sheet metal dam which is located within the sump of the cooler. A oneway check valve is located in the wall of the dam so that water is free to flow from the main reservoir portion of the sump into the relatively smaller dam portion but is prevented from flowing in a reverse direction. A pump and siphon valve are located inside the dam and a float controlled water inlet valve is located in the main reservoir portion of the sump to maintain the water level in the sump and in the dam, due to the free flow through the checking valve, at a predetermined level. During operation of the cooler, the pump delivers water from the dam portion to the cooler's water distribution system which in turn supplies water to the cooler pads, and the unevaporated water will return from the pads, by gravity, to the main reservoir portion of the sump. When the pump is turned off, water in the cooler's water distribution system will drain back into the dam area only, due to the reverse flow checking provided by the check valve, thus raising the water level therein to a point where it primes the siphon valve. When the siphon valve is so primed, water in the dam will be drained therefrom and the water in the main reservoir portion of the sump will flow through the check valve into the dam and will exit the dam through the siphon valve. When the water supply is left on during such an operation, the result is that a draining, flushing and water replacement action takes place, and due to the outlet and siphon valve being sized to drain the sump at a faster rate than the water inlet line can replace the water, the water level will drop until the siphon valve looses its prime, whereupon refilling of the sump with fresh water takes place under control of the float operated inlet valve. This same operation occurring when the water supply to the cooler is shutoff results in draining of most of the water from the sump.
This particular prior art flushing and draining device has not received commercial acceptance for several reasons. In the first place, the amount of water contained in the water distribution plumbing system of an evaporative cooler is quite small and will, in most cases, be insufficient to achieve priming of the siphon valve. Secondly, the check valve of this prior art structure is a constant source of problems, in that the water pressure differential on the opposite sides thereof is all that can be relied upon for opening and closing of the valve, and that pressure differential is exceedingly small. The small pressure differential relied on to open and close the check valve precludes the use of a spring or other device to bias the valve toward its closed position. Therefore, the check valve is a passive rather than a positively acting device, and achieving a fully closed position when such a state is critical is oftentimes not achieved. To illustrate this point, there can be no leakage through the check valve when the draining cycle is initiated in that such leakage would prevent the water level in the dam from reaching the point where the siphon valve is primed. In addition to the passive action of the check valve, it by necessity, is operated under water and this subjects the valve to corrosion, scaling and the like, and the valve is often jammed by foreign matter such as dirt, wood shavings from the excelsior pads and the like. Thirdly, this prior art device is incapable of completely draining all of the water from the dam and the main reservoir portion of the sump in that both the check valve and the inlet to the siphon valve are spaced upwardly from the bottom of the sump. Therefore, the desirability of draining the sump when the cooler is inoperative cannot be completely achieved and a relatively large surface area of water will remain. Further, when the pump is shutoff to accomplish a draining, flushing and water replacement cycle, water will not be supplied to the cooler pads for a considerable length of time due to the amount of water that must be drained and replaced to fill the entire relatively large sump before normal operation can be resumed. Since warm air will continue to be drawn through the pads by the air handler during such a cycle, the pads will dry out rather rapidly, and upon drying, dust, dirt and the like, will be extracted from the pads by the aid moving therethrough.
In addition to the inherent problems of this particular prior art structure, it does nothing to remove the cooler components from direct exposure to the water in the sump either during operation or during nonuse of the evaporative cooler, and is incapable of automatically draining rain water, or the like which enters the cooler during nonuse periods.
Therefore, a need exists for a new and improved automatic flushing and draining apparatus for evaporative coolers which overcomes some of the problems and shortcomings of the prior art.